Impact/Purpose:

Purpose of this research was to measure the temperature offsets that exist on the Sunset Laboratory Carbon Analyzer and to investigate the influece of temperature calibration on the concentration of each carbon fraction and sub-fraction measured by the NIOSH 5040 and IMPROVE protocols.

Description:

The Sunset Laboratory Dual-Optical Carbonaceous Analyzer that simultaneously measures transmission and reflectance signals is widely used in thermal-optical analysis of particulate matter samples. Most often it is used to measure total carbon (TC), organic carbon (OC), and elemental carbon (EC) fractions, but also the thermal sub-fractions of OC and EC for source identification purposes.
However, previous studies (1, 2) showed that the sample (filter) temperature and temperature measured by the thermocouple (or setpoint temperature) can differ by 10 to 50 ˚C. Hence, that temperature disagreement might substantially affect the OC/EC split and further the OC and EC concentrations. Since the temperature precision in thermal-optical analysis is highly desired, the Sunset Laboratory developed a temperature calibration procedure for the temperature sensor built into the front oven of the instrument. That simple procedure significantly reduced the temperature differences between the setpoint temperatures and the sample (filter) temperatures, thus providing more confidence in the results. In addition, this method also improves the inter-laboratory comparisons. Therefore, our experiments thoroughly investigated and clearly showed the need of temperature calibration on the each Sunset Carbon Analyzer to obtain accurate filter temperatures, improve comparability of OC and EC fractions and sub-fractions, and make the method more reliable in source apportionment studies.
Temperature calibrations were performed at NIOSH 5040 and IMPROVE temperature operating conditions to determine the filter/setpoint temperature relationships for both methods. The measured temperatures and the differences between the setpoint and filter temperatures for both methods were investigated. Along with those results, the differences between TC, OC, and EC fractions, as well as OC and EC sub-fractions, before and after temperature calibrations for both temperature protocols were also investigated.
1. Phuah, C. H., Peterson, M. R., Richards, M. H., Turner, J. H., Dillner, A. M. (2009). A temperature calibration procedure for the Sunset Laboratory carbon aerosol analysis lab instrument, Aerosol Science and Technology, 43, 1013-1021.
2. Chow, J. C., Watson, J. G., Chen, L.-W., A., Peredes-Miranda, G., Chang, M.-C., O., Trimble, D., Fung, K. K., Zhang, H., Zhen Yu, J. (2002). Refining temperature measures in thermal/optical carbon analysis, Atmospheric chemistry and physics, 5, 2961-2972.

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Record Details:

Record Type: DOCUMENT (PRESENTATION/SLIDE)

Product Published Date: 10/08/2012

Record Last Revised: 03/17/2015

OMB Category: Other

Record ID: 307282

Organization:

U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL RISK MANAGEMENT RESEARCH LABORATORY
AIR POLLUTION PREVENTION AND CONTROL DIVISION
EMISSIONS CHARACTERIZATION AND PREVENTION BRANCH